Skin lightening agents, compositions and methods

ABSTRACT

Disclosed are coumarin derived compounds of formula I as skin lightening agents alone or in combination with other skin benefit agents and together with a cosmetic vehicle: 
                         
Where each or both R 1  and/or R 2  represents hydrogen (H); linear or branched, saturated or unsaturated C 1 -C 12  alkyl, alkenyl, acyl, or heteroalkyl (preferably, alkoxy) groups; and
 
R 3  represents linear or branched, cyclic or acyclic, saturated or unsaturated C 1 -C 12  alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heteroalkyl group; and
 
R 4  represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated, containing or not containing a heteroatom C 1 -C 22  alkyl, alkenyl, cycloalkyl, cycloalkenyl, heteroalkyl, aryl, or heteroaryl group. In a most preferred embodiment, each R 1 , R 2  and R 4  represent H, while R 3  represents a methyl group, referred to herein as a 4-methyl 7-hydroxy-coumarin derivative, or coumarin derived resorcinol derivative, which may be prepared by catalytic (nickel or paladium catalyst) hydrogenation of 4-methyl 7-hydroxy-coumarin followed by hydrolysis. The inventive compounds, compositions and methods have effective skin lightening properties, may be less irritating to the skin, and are cost-effective and relatively simple to manufacture.
 
     Also disclosed are processes for making the inventive compounds of general formula I from 4-substituted-7-hydroxy coumarin derivatives.

FIELD OF THE INVENTION

The invention relates to coumarin derived compounds and cosmetic compositions including same, and more specifically, 4-substituted 7-hydroxy coumarin derived compounds, and their cosmetic use, such as skin lightening agents.

BACKGROUND OF THE INVENTION

Many people are concerned with the degree of pigmentation of their skin. For example, people with age spots or freckles may wish such pigmented spots to be less pronounced. Others may wish to reduce the skin darkening caused by exposure to sunlight or to lighten their natural skin color. To meet this need, many attempts have been made to develop products that reduce the pigment production in the melanocytes. However, the substances identified thus far tend to have either low efficacy or undesirable side effects, such as, for example, toxicity or skin irritation. Therefore, there is a continuing need for new skin lightening agents, with improved overall effectiveness, as well as agents that lend themselves to ease of processing in their manufacture.

Resorcinol derivatives have cosmetic skin and hair benefits. Certain resorcinol derivatives, particularly 4-substituted resorcinol derivatives, are useful in cosmetic compositions for skin lightening benefits. Resorcinol derivatives are described in many publications, including U.S. Pat. No. 4,959,393; Hu et al., U.S. Pat. No. 6,132,740; Bradley, et al., U.S. Pat. No. 6,504,037; and Japanese published patent applications JP 2001-010925 and JP2000-327557. Resorcinol derivatives are known compounds and can be readily obtained by various means, including by a method wherein a saturated carboxylic acid and resorcinol are condensed in the presence of zinc chloride and the resultant condensate is reduced with zinc amalgam/hydrochloric acid (Lille, et al., Tr. Nauch-Issled. Inst. Slantsev 1969, No. 18:127-134), or by a method wherein resorcinol and a corresponding alkyl alcohol are reacted in the presence of an alumina catalyst at a high temperature of from 200 to 400° C. (British Patent No. 1,581,428). Skin lightening compounds that may be derived from coumarin are disclosed in Applicants' co-pending patent application Ser. No. 10/227,642 filed Aug. 23, 2002. Some of these compounds can be irritating to the skin.

Applicants have now discovered that the use of compounds that which may be derived from coumarin derivatives (although not limited to such process), deliver skin lightening benefits. The general chemical formulas and structures of these compounds are discussed in more detail herein below. Hydroxy coumarin derived compounds, and especially 4-substituted 7-hydroxy-coumarin derived compounds which resemble resorcinol derivatives, have been found to be effective and possibly less irritating to the skin and are relatively simple to manufacture. These compounds are referred to herein as “coumarin derived resorcinol derivatives.” Coumarin derived resorcinol derivatives of the present invention have not been used for personal care or, in particular, for lightening skin.

SUMMARY OF THE INVENTION

Compounds of the general formula I and compositions including same deliver cosmetic benefits, particularly skin lightening benefits, with potential reduced irritation and relative ease of manufacture. The present invention provides a cosmetic method of skin lightening using a composition comprising in addition to a cosmetically acceptable vehicle, about 0.000001 to about 50% of a compound of formula I,

Where each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁- C₁₂ alkyl, alkenyl, acyl, or heteroalkyl (e.g., preferably, alkoxy) groups. Preferably, each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁- C₁₂ alkyl or acyl groups. More preferably, both R₁ and R₂ represent hydrogen; and R₃ represents linear or branched, cyclic or acyclic, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heteroalkyl group. Preferably, R₃ represents an alkyl group. More preferably, R₃ represents a C₁ alkyl group (i.e, methyl group); and R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated; containing or not containing a heteroatom (e.g. furans, dihydrofurans, pyrans) C₁-C₂₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, heteroalkyl; aryl, or heteroaryl group. Preferably, R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated C₁-C₂₂ alkyl group. In a more preferred embodiment, R₄ represents H.

In a most preferred embodiment, each R₁, R₂ and R₄ represent H, while R₃ represents a methyl group, i.e. Compound of formula II herein.

These inventive 4-methyl 7-hydroxy-coumarin derived compounds, or coumarin derived resorcinol derivatives, may be prepared by catalytic (nickel or paladium catalyst) hydrogenation of 4-substituted 7-hydroxy-coumarin followed by hydrolysis. The hydroxy groups (where any of R₁, R₂ and R₄ represents H) may be further substituted by methods known in the art, such as by esterification.

Further skin benefit agents may be included in the compositions and inventive method, such as alpha-hydroxy acids, beta-hydroxy acids, polyhydroxy acids, hydroquinone, t-butyl hydroquinone, Vitamin C derivatives, dioic acids, retinoids, resorcinol derivatives, and mixtures thereof. Organic and inorganic sunscreens may also be included.

The inventive compositions and methods have effective skin lightening properties, may be less irritating to the skin, and are cost-effective and relatively simple to manufacture.

DETAILED DESCRIPTION OF THE INVENTION

The use of the inventive compounds that which may be derived from coumarin derivatives (although not limited to such process), deliver skin lightening benefits. The general chemical formulas and structures of these compounds are discussed in more detail herein below. The 4-substituted 7-hydroxy-coumarin derived compounds have been found to be effective cosmetic agents, particularly, skin lightening agents, and are relatively simple to produce.

As used herein, the term “cosmetic composition” is intended to describe compositions for topical application to human skin.

The term “skin” as used herein includes the skin on the face, neck, chest, back, arms, axilla, hands, legs, and scalp.

Except in the examples, or where otherwise explicitly indicated, all numbers in this description indicating amounts of material or conditions of reaction, physical properties of materials and/or use are to be understood as modified by the word “about”. All amounts are by weight of the composition, unless otherwise specified.

It should be noted that in specifying any range of concentration, any particular upper concentration can be associated with any particular lower concentration.

For the avoidance of doubt the word “comprising” is intended to mean including but not necessarily consisting of or composed of. In otherwords the listed steps or options need not be exhaustive.

Skin Lightening Agents

The invention is concerned with compounds of general formula I, shown below, compositions including same, and their cosmetic use, particularly as skin lightening agents. A particular advantage of the inventive compositions and methods is that compounds of general formula I can be less irritating to the skin than other skin lightening compounds, even those with similar structure, and are relatively easy to manufacture:

Where each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, acyl, or heteroalkyl (preferably, alkoxy) groups. Preferably, each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁-C₁₂ alkyl or acyl groups. More preferably, both R₁ and R₂ represent hydrogen; and R₃ represents linear or branched, cyclic or acyclic, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heteroalkyl group. Preferably, R₃ represents a C₁-C₁₂ alkyl group, more preferably, a C₁ alkyl group (i.e, methyl group); and R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated, containing or not containing a heteroatom (e.g. furans, dihydrofurans, pyrans) C₁-C₂₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, heteroalkyl, aryl, or heteroaryl group. Preferably, R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated C₁-C₂₂ alkyl group. In a more preferred embodiment, R₄ represents H.

In a most preferred embodiment, each R₁, R₂ and R₄ represent H, while R₃ represents a methyl group. This most preferred embodiment is represented by compound of formula II:

Process. This most preferred embodiment, referred to herein as a 4-methyl 7-hydroxy-coumarin derived compound, or coumarin derived resorcinol derivative, may be prepared by catalytic (nickel or paladium catalyst, preferably Pd on carbon substrate, i.e., Pd/C) hydrogenation of 4-methyl 7-hydroxy-coumarin followed by hydrolysis. The hydroxy groups (where any of R₁, R₂ and R₄ represents H) may be further substituted by methods known in the art, such as by esterification. Other methods of deriving the inventive compounds may also be available and the invention is not limited by the method of preparation.

The compositions generally contain about 0.000001 to about 50% of coumarin derived compounds of general formula I. Compounds of formula II are preferred. The amount of the coumarin derived compounds is preferably in the range of about 0.00001% to about 10%, more preferably about 0.001 to about 7%, most preferably from 0.01 to about 5%, of the total amount of a cosmetic composition.

Further skin benefit agents may be included in the compositions useful for the inventive method. Organic and inorganic sunscreens may also be included.

The inventive compositions and methods have effective skin lightening properties, may be less irritating to the skin, and are cost-effective and relatively simple to manufacture.

Process Synthetic Procedures

I. Hydrogenation of 4-Substituted-7-hydroxycoumarins

General Procedure

A high pressure reaction vessel is charged with Compound of general formula A, a 4-substituted-7-hydroxycoumarin (preferably, 4-alkyl-7-hydroxy coumarin), in a suitable solvent (e.g., acetic acid, alcohol, organic solvents and mixtures thereof and a catalyst is added (e.g., homogeneous or heterogeneous catalysts such as Pd and/or Ni attached to a suitable matrix and mixtures thereof. The reactor is pressurized with hydrogen (e.g., about 100 to about 800 psi) and stirred above about 25° C. (e.g., about 25° C. to about 60° C.) until complete consumption of 4-substituted-7-hy coumarin (preferably, 4-alkyl-7-hydroxy coumarin) is observed as monitored using a suitable analytical method (e.g., TLC, GC, LC, hydrogen consumption, and combinations thereof. The reaction mixture is filtered through an insoluble support (e.g., celite, silica gel, and combinations thereof, the solvents removed under reduced pressure and the product purified using purification methods such as, for example, re-crystallization, distillation, and combinations thereof.

Specific Procedure/Preferred Embodiment: 7-hydroxy-3,4-dihydro-4-methylcoumarin (B1)

A Parr hydrogenator (1 L) was charged with 7-hydroxy-4-methylcoumarin, i.e., Compound of formula A1, (60 g, 0.34 mol) and acetic acid (350 ml). A suspension of 10% Pd/C (6.0 g) in acetic acid (150 ml) was added and the reactor sealed, evacuated and purged with nitrogen (4×). The reactor was pressurized to 320 psi with hydrogen and stirred at 30° C. for 16 hr, at which point no hydrogen was consumed and TLC (4% methanol:chloroform) showed the clean formation of product at the expense of starting material. The reactor was evacuated, purged with nitrogen and the mixture filtered through celite. The solvent was removed to give a white solid (60.5 g, 100%). Recrystallization from ethyl acetate:hexane afforded pure product as a white solid: m.p. 109-110° C.; ¹H NMR (DMSO-d₆) d 1.19 (d, JJ=6.7, 3H), 2.52 (dd, JJ=15.9, 7.3, 1H), 2.84 (dd, JJ=15.9, 5.5, 1H), 3.08 (m, 1H), 6.46 (d, JJ=2.4, 1H), 6.58 (dd, JJ=8.2, 2.4, 1H), 7.10 (d, JJ=8.2, 1H), 9.66 (s, 1H); ¹³C (DMSO-d₆) d 19.84, 27.87, 36.45, 103.17, 111.38, 118.29, 127.17, 151.45, 157.17, 168.11; m/z (EI; TMS derivatized; M⁺) 250; IR (neat; cm⁻¹) 3379.6, 2969.2, 2930.2, 2871.5, 1748.0, 1630.7, 1601.4, 1518.4, 1454.89, 1352.3, 1283.9, 1249.7, 1239.9, 1152.0, 1117.8, 1078.7, 1020.1, 995.7, 942.0, 854.0, 814.9.

II. Hydrolysis of 4-Substituted-3,4-dihydro-7-hydroxycoumarins

General Procedure

The Compound of general formula B, i.e., 4-substituted-3,4-dihydro-7-hydroxycoumarin, is suspended in water and a hydroxide ion equivalent reagent is added (e.g., sodium hydroxide, potassium hydroxide, polymer-bound carbonate, and combinations thereof. The reaction is monitored using a suitable analytical method (e.g., TLC, GC, LC, and combinations thereof until complete consumption of the starting material. The reaction mixture is cooled down (e.g., temperatures between about 0 and about 10° C.) and acidified with a hydrogen ion equivalent reagent (e.g., hydrochloric acid) until the pH of the solution reaches 1 or below. The solution is extracted with a suitable organic solvent (e.g., diethyl ether), the organic layer dried using an insoluble drying agent (e.g., sodium sulfate), filtered and the solvent removed. The product is purified using purification methods such as, for example, re-crystallization, distillation, chromatography, or combination thereof.

Specific Procedure/Preferred Embodiment: 3-(2,4-dihydroxyphenyl)-butyric acid (Compound of General Formula II)

Sodium hydroxide (5.0 M, 27 ml, 135 mmol) was added to a suspension of 7-hydroxy-3,4-dihydro-4-methylcoumarin (Compound of formula B1) (8.0 g, 45 mmol) in water (40 ml) at room temperature and the resulting solution stirred for 20 min. At this time, TLC (4% methanol:chloroform) showed the clean formation of product at the expense of starting material. The solution was cooled to 5° C. and carefully acidified with concentrated HCl to pH less than about 1, keeping the temperature at less than about 15° C. throughout the addition. The solution was extracted with ethyl ether (4×100 ml), the organic layers washed with saturated NaCl (4×50 ml), combined, dried (Na₂SO₄), filtered and the solvent removed to give a pale orange oil. Further purification by filtering through a short pad of silica gel and eluting with ethyl acetate afforded pure product as a white solid (8.3 g, 94%): m.p. 92-94° C.; ¹H NMR (DMSO-d₆) d 1.13 (d, JJ=7.0, 3H), 2.33 (dd, JJ=15.0, 8.9, 1H), 2.52 (dd, JJ=15.5, 7.3, 1H), 3.32 (m, 1H), 6.16 (dd, JJ=8.2, 2.4, 1H), 6.28 (d, JJ=2.4, 1H), 6.84 (d, JJ=8.2, 1H), 9.08 (s, 1H), 9.59 (s, 1H), 11.87 (s, 1H); ¹³C NMR (DMSO-d₆) d 20.39, 28.97, 41.0, 102.58, 106.01, 122.55, 127.27, 155.19, 156.18, 173.74; m/z (EI; TMS derivatized; M⁺) 412; IR (neat; cm⁻¹) 3360.1, 2974.1, 2935.1, 2876.4, 1748.0, 1713.8, 1625.9, 1606.3, 1518.4, 1459.8, 1381.6, 1347.4, 1283.9, 1254.6, 1239.9, 1156.9, 1117.8, 1025.0, 981.0, 937.1, 849.1, 810.1.

III. Esterification of 4-Substituted-3,4-dihydro-7-hydroxycoumarins

General Procedure

The Compound of general formula B, i.e., 4-substituted-3,4-dihydro-7-hydroxycoumarin, is dissolved in the alcohol of choice or, alternately, the coumarin and the alcohol are dissolved in a suitable solvent (e.g., tetrahydrofuran). An acid catalyst is added (e.g., sulfuric acid, acidic resin, or combinations thereof and the reaction is monitored using a suitable analytical method (e.g., TLC, GC, LC, or combinations thereof) until complete consumption of the starting material. The reaction mixture is partly neutralized (to pH of about 4 to about 7) with mild base (e.g., aqueous sodium bicarbonate) and partitioned between a suitable organic solvent (e.g., diethyl ether) and water. The organic layer is dried using an insoluble drying agent (e.g., sodium sulfate), filtered and the solvent removed under reduced pressure. The product is purified using purification methods such as, for example, re-crystallization, distillation, chromatography, and/or combinations thereof.

Specific Procedure/Preferred Embodiment: Methyl 3-(2,4-dihydroxyphenyl)-butyrate (D1)

Concentrated sulfuric acid (1.2 mL, 43 mmol) was added to a solution of 7-hydroxy-3,4-dihydro-4-methylcoumarin (B1) (75.8 g, 430 mmol) in methanol (1 L) at room temperature and the solution stirred for about 16 hours. At this time, TLC (8% methanol:chloroform) showed the clean formation of product at the expense of starting material. The solution was neutralized with 7% NaHCO₃ solution (50 ml) and the majority of the solvent (750 ml) removed under reduced pressure. The solution was diluted with ethyl acetate (1 L), washed successively with saturated NaHCO₃: saturated NaCl (1:1, 200 ml), saturated NaCl (2×200 ml), dried (Na₂SO₄), filtered and the solvent removed to give an orange oil. Further purification by filtering through a short pad of silica gel and eluting with 5% methanol in chloroform afforded pure product as a pale orange gel (87 g, 98%): ¹H NMR (DMSO-d₆) d 1.13 (d, JJ=7.0, 3H), 2.42 (dd, JJ=15.0, 8.9, 1H), 2.58 (dd, JJ=15.0, 5.8, 1H), 3.37 (m, 1H), 3.55 (s, 3H), 6.15 (dd, JJ=8.6, 2.4, 1H), 6.28 (d, JJ=2.4, 1H), 6.84 (d, JJ=8.2, 1H), 8.93 (s, 1H), 9.11 (s, 1H); ¹³C NMR (DMSO-d₆) d 20.16, 29.09, 40.77, 51.00, 102.55, 106.02, 122.09, 127.04, 155.18, 156.27, 172.55; m/z (EI; TMS derivatized; M⁺) 354; IR (neat; cm⁻¹) 3384.5, 2969.3, 1708.9, 1621.0, 1606.3, 1518.4, 1454.9, 1367.0, 1303.5, 1220.4, 1166.7, 1108.1, 976.2, 839.4, 810.1.

Optional Skin Benefit Agents

Preferred cosmetic compositions are those suitable for the application to human skin according to the method of the present invention, which optionally, but preferably, include a skin benefit agent in addition to the inventive coumarin derived compounds.

Suitable additional skin benefit agents include anti-aging, wrinkle-reducing, skin whitening, anti-acne, and sebum reduction agents. Examples of these include alpha-hydroxy acids, beta-hydroxy acids, polyhydroxy acids, hydroquinone, t-butyl hydroquinone, Vitamic C derivatives, dioic acids, retinoids; betulinic acid; allantoin, a placenta extract; and other resorcinol derivatives.

Cosmetically Acceptable Carrier

The cosmetically acceptable vehicle may act as a dilutant, dispersant or carrier for the skin benefit ingredients in the composition, so as to facilitate their distribution when the composition is applied to the skin.

The vehicle may be aqueous, anhydrous or an emulsion. Preferably, the compositions are aqueous or an emulsion, especially water-in-oil or oil-in-water emulsion, preferentially oil in water emulsion. Water when present will be in amounts which may range from 5 to 99%, preferably from 20 to 70%, optimally between 40 and 70% by weight.

Besides water, relatively volatile solvents may also serve as carriers within compositions of the present invention. Most preferred are monohydric C₁-C₃ alkanols. These include ethyl alcohol, methyl alcohol and isopropyl alcohol. The amount of monohydric alkanol may range from 1 to 70%, preferably from 10 to 50%, optimally between 15 to 40% by weight.

Emollient materials may also serve as cosmetically acceptable carriers. These may be in the form of silicone oils and synthetic esters. Amounts of the emollients may range anywhere from 0.1 to 50%, preferably between 1 and 20% by weight.

Silicone oils may be divided into the volatile and non-volatile variety. The term “volatile” as used herein refers to those materials which have a measurable vapor pressure at ambient temperature. Volatile silicone oils are preferably chosen from cyclic or linear polydimethylsiloxanes containing from 3 to 9, preferably from 4 to 5, silicon atoms. Linear volatile silicone materials generally have viscosities less than about 5 centistokes at 25° C. while cyclic materials typically have viscosities of less than about 10 centistokes. Nonvolatile silicone oils useful as an emollient material include polyalkyl siloxanes, polyalkylaryl siloxanes and polyether siloxane copolymers. The essentially non-volatile polyalkyl siloxanes useful herein include, for example, polydimethyl siloxanes with viscosities of from about 5 to about 25 million centistokes at 25° C. Among the preferred non-volatile emollients useful in the present compositions are the polydimethyl siloxanes having viscosities from about 10 to about 400 centistokes at 25° C.

Among the ester emollients are:

-   -   (1) Alkenyl or alkyl esters of fatty acids having 10 to 20         carbon atoms. Examples thereof include isoarachidyl         neopentanoate, isononyl isonanonoate, oleyl myristate, oleyl         stearate, and oleyl oleate.     -   (2) Ether-esters such as fatty acid esters of ethoxylated fatty         alcohols.     -   (3) Polyhydric alcohol esters. Ethylene glycol mono and di-fatty         acid esters, diethylene glycol mono- and di-fatty acid esters,         polyethylene glycol (200-6000) mono- and di-fatty acid esters,         propylene glycol mono- and di-fatty acid esters, polypropylene         glycol 2000 monooleate, polypropylene glycol 2000 monostearate,         ethoxylated propylene glycol monostearate, glyceryl mono- and         di-fatty acid esters, polyglycerol poly-fatty esters,         ethoxylated glyceryl monostearate, 1,3-butylene glycol         monostearate, 1,3-butylene glycol distearate, polyoxyethylene         polyol fatty acid ester, sorbitan fatty acid esters, and         polyoxyethylene sorbitan fatty acid esters are satisfactory         polyhydric alcohol esters.     -   (4) Wax esters such as beeswax, spermaceti, myristyl myristate,         stearyl stearate and arachidyl behenate.     -   (5) Sterol esters, of which cholesterol fatty acid esters are         examples.

Fatty acids having from 10 to 30 carbon atoms may also be included as cosmetically acceptable carriers for compositions of this invention. Illustrative of this category are pelargonic, lauric, myristic, palmitic, stearic, isostearic, hydroxystearic, oleic, linoleic, ricinoleic, arachidic, behenic and erucic acids.

Humectants of the polyhydric alcohol-type may also be employed as cosmetically acceptable carriers in compositions of this invention. The humectant aids in increasing the effectiveness of the emollient, reduces scaling, stimulates removal of built-up scale and improves skin feel. Typical polyhydric alcohols include glycerol, polyalkylene glycols and more preferably alkylene polyols and their derivatives, including propylene glycol, dipropylene glycol, polypropylene glycol, polyethylene glycol and derivatives thereof, sorbitol, hydroxypropyl sorbitol, hexylene glycol, 1,3-butylene glycol, 1,2,6-hexanetriol, ethoxylated glycerol, propoxylated glycerol and mixtures thereof. For best results the humectant is preferably propylene glycol or sodium hyaluronate. The amount of humectant may range anywhere from 0.5 to 30%, preferably between 1 and 15% by weight of the composition.

Thickeners may also be utilized as part of the cosmetically acceptable carrier of compositions according to the present invention. Typical thickeners include crosslinked acrylates (e.g. Carbopol 982), hydrophobically-modified acrylates (e.g. Carbopol 1382), cellulosic derivatives and natural gums. Among useful cellulosic derivatives are sodium carboxymethylcellulose, hydroxypropyl methylcellulose, hydroxypropyl cellulose, hydroxyethyl cellulose, ethyl cellulose and hydroxymethyl cellulose. Natural gums suitable for the present invention include guar, xanthan, sclerotium, carrageenan, pectin and combinations of these gums. Amounts of the thickener may range from 0.0001 to 5%, usually from 0.001 to 1%, optimally from 0.01 to 0.5% by weight.

Collectively the water, solvents, silicones, esters, fatty acids, humectants and/or thickeners will constitute the cosmetically acceptable carrier in amounts from 1 to 99.9%, preferably from 80 to 99% by weight.

An oil or oily material may be present, together with an emulsifier to provide either a water-in-oil emulsion or an oil-in-water emulsion, depending largely on the average hydrophilic-lipophilic balance (HLB) of the emulsifier employed.

Surfactants may also be present in cosmetic compositions of the present invention. Total concentration of the surfactant will range from 0.1 to 40%, preferably from 1 to 20%, optimally from 1 to 5% by weight of the composition. The surfactant may be selected from the group consisting of anionic, nonionic, cationic and amphoteric actives. Particularly preferred nonionic surfactants are those with a C₁₀-C₂₀ fatty alcohol or acid hydrophobe condensed with from 2 to 100 moles of ethylene oxide or propylene oxide per mole of hydrophobe; C₂-C₁₀ alkyl phenols condensed with from 2 to 20 moles of alkylene oxide; mono- and di-fatty acid esters of ethylene glycol; fatty acid monoglyceride; sorbitan, mono- and di-C₈-C₂₀ fatty acids; block copolymers (ethylene oxide/propylene oxide); and polyoxyethylene sorbitan as well as combinations thereof. Alkyl polyglycosides and saccharide fatty amides (e.g. methyl gluconamides) are also suitable nonionic surfactants.

Preferred anionic surfactants include soap, alkyl ether sulfate and sulfonates, alkyl sulfates and sulfonates, alkylbenzene sulfonates, alkyl and dialkyl sulfosuccinates, C₈-C₂₀ acyl isethionates, acyl glutamates, C₈-C₂₀ alkyl ether phosphates and combinations thereof.

Optional Components

In the cosmetic compositions of the invention, there may be optionally added plasticizers; calamine; antioxidants; chelating agents; as well as sunscreens.

Other adjunct minor components may also be incorporated into the cosmetic compositions. These ingredients may include coloring agents, pigments, opacifiers, and perfumes. Amounts of these other adjunct minor components may range anywhere from 0.001% up to 20% by weight of the composition.

Sunscreens. For use as sunscreen, metal oxides may be used alone or in mixture and/or in combination with organic sunscreens. Examples of organic sunscreens include but are not limited those set forth in the table below.

The amount of the organic sunscreens in the cosmetic composition is preferably in the range of about 0.1 wt % to about 10 wt %, more preferably about 1 wt % to 5 wt %. Preferred organic sunscreens are PARSOL MCX and Parsol 1789, due to their effectiveness and commercial availability.

TABLE 3 CTFA Name Trade Name Supplier Benzophenone-3 UVINUL M-40 BASF Chemical Co. Benzophenone-4 UVINUL MS-40 BASF Chemical Co. Benzophenone-8 SPECRA-SORB American Cyanamide UV-24 DEA Methoxycinnamate BERNEL HYDRO Bernel Chemical Ethyl dihydroxypropyl- AMERSCREEN P Amerchol Corp. PABA Glyceryl PABA NIPA G.M.P.A. Nipa Labs. Homosalate KEMESTER HMS Hunko Chemical Methyl anthranilate SUNAROME UVA Felton Worldwide Octocrylene UVINUL N-539 BASF Chemical Co. Octyl dimethyl AMERSCOL Amerchol Corp. PABA Octyl PARSOL MCX Bernel Chemical methoxycinnamate Octyl salicylate SUNAROME Felton Worldwide WMO PABA PABA National Starch 2-Phenylbenzimidazole-5- EUSOLEX 232 EM Industries sulphonic acid TEA salicylate SUNAROME W Felton Worldwide 3-(4-methylbenzylidene)- EUSOLEX 6300 EM Industries camphor Benzophenone-1 UVINUL 400 BASF Chemical Co. Benzophenone-2 UVINUL D-50 BASF Chemical Co. Benzophenone-6 UVINUL D-49 BASF Chemical Co. Benzophenone-12 UVINUL 408 BASF Chemical Co. 4-Isopropyl dibenzoyl EUSOLEX 8020 EM Industries methane Butyl methoxy dibenzoyl PARSOL 1789 Givaudan Corp. methane Etocrylene UVINUL N-35 BASF Chemical Co.

Use of the Composition

The method according to the invention is intended primarily as using a personal care product for topical application to human skin, as well as to lighten the skin, to reduce the degree of pigmentation in the skin, or to even the skin tone.

In use, a small quantity of the composition, for example from 1 to 5 ml, is applied to exposed areas of the skin, from a suitable container or applicator and, if necessary, it is then spread over and/or rubbed into the skin using the hand or fingers or a suitable device.

Product Form and Packaging

The cosmetic composition of the invention can be formulated as a lotion having a viscosity of from 4,000 to 10,000 mPas, a fluid cream having a viscosity of from 10,000 to 20, 000 mPas, or a cream having a viscosity of from 20,000 to 100,000 mPas or above. The composition can be packaged in a suitable container to suit its viscosity and intended use by the consumer. For example, a lotion or fluid cream can be packaged in a bottle or a roll-ball applicator or a propellant-driven aerosol device or a container fitted with a pump suitable for finger operation. When the composition is a cream, it can simply be stored in a non-deformable bottle or squeeze container, such as a tube or a lidded jar. When the composition is a solid or semi-solid stick, it may be packaged in a suitable container for manually or mechanically pushing out or extruding the composition.

The invention accordingly also provides a closed container containing a cosmetically acceptable composition as herein defined.

The following examples are by way of example, not by way of limitation, of the principles of the present invention, to illustrate the best mode of carrying out the invention.

EXAMPLE 1

The following compounds were used throughout the examples that follow. These compounds were prepared in accordance with the procedures set forth in this Example 1.

The compound of formula A1, referred to herein as 4-methyl 7-hydroxy coumarin was used as a starting material to prepare the coumarin derived resorcinol compounds according to the present invention.

EXAMPLE 2

Cosmetic compositions within the scope of the invention were prepared.

A base formulation shown in the Table below was made by heating phase A ingredients to 70 to 85° C. with stirring. Phase B ingredients were heated in a separate container to 70 to 85° C. with stirring. Then, phase A was added into phase B while both phases were kept at 70 to 85° C. The mixture was stirred for at least 15 minutes at 70 to 85° C., then cooled.

TABLE 4 a b Ingredients % wt. % wt. Phase Isostearyl Palmitate 6.00 6.00 A C12-C15 Alkyl Octanoate 3.00 3.00 A PEG-100 Stearate 2.00 2.00 A Glyceryl Hydroxystearate 1.50 1.50 A Stearyl Alcohol 1.50 1.50 A Stearic acid 3.00 4.00 A TEA, 99% 1.20 1.20 B Dimethicone 1.00 1.00 A Sorbitan Monostearate 1.00 1.00 A Magnesium Aluminum Silicate 0.60 0.60 B Vitamin E acetate 0.10 0.10 A Cholesterol 0.50 0.50 A Simethicone 0.01 0.01 B Xanthan gum 0.20 0.20 B Hydroxyethylcellulose 0.50 0.50 B Propylparaben 0.10 0.10 B Disodium EDTA 0.05 0.05 B Butylated hydroxytolene 0.05 0.05 B Compound of formula II 0.05 2.00 B Niacinamide 1.00 1.00 B Metal oxide 2.50 5.00 B Methylparaben 0.15 0.15 B Water BAL* BAL* B Total 100.00 100.00 B *BAL means Balance.

EXAMPLE 3

Additional cosmetic compositions within the scope of the invention were prepared.

TABLE 5 Component Wt % Phase water, DI BALANCE A disodium EDTA 0.05 A magnesium aluminum silicate 0.6 A methyl paraben 0.15 A simethicone 0.01 A butylene glycol 1,3 3.0 A hydroxyethylcellulose 0.5 A glycerine, USP 2.0 A xanthan gum 0.2 A triethanolamine 1.2 B stearic acid 3.0 B propyl paraben NF 0.1 B glyceryl hydroxystearate 1.5 B stearyl alcohol 1.5 B isostearyl palmitate 6.0 B C12-15 alcohols octanoate 3.0 B dimethicone 1.0 B cholesterol NF 0.5 B sorbitan stearate 1.0 B Micronized titanium dioxide 5.0 C tocopheryl acetate 0.1 B PEG-100 stearate 2.0 B sodium stearoyl lactylate 0.5 B hydroxycaprylic acid 0.1 C Compound of formula II 10.0 C PARSOL MCX 2.4 C alpha-bisabolol 0.2 C

The composition of Example 3, was prepared as follows:

-   -   1. Heat Phase A to 80° C.     -   2. Heat Phase B to 75° C. in a separate container     -   3. Add B to A and mix with heat off for 30 min.     -   4. At 50° C. add Phase C and mix for 10 min.

EXAMPLES 4-11

A set of additional compositions useful in the methods of the present invention were prepared within the scope of the present invention and are listed in the table below.

TABLE 6 Examples (wt. %) 4 acid Ingredients Phase soap base 5 6 7 8 9 10 11 Stearic acid A 17.9 17.9 17.9 17.9 17.9 17.9 17.9 17.9 Sodium cetearyl A 2.2 1 1.5 2 3 2 sulfate* (emulsifier) Myrj 59* A 2 2 2 2 2 1 (emulsifier) Span 60* A 2 2 2 2 2 1 (emulsifiers) Compound of B 0.05 0.05 2.0 2.0 3.5 3.5 5.0 10.0 formula II Micronized Zinc B 2.50 5.00 5.00 2.50 2.50 5.00 2.50 5.00 Oxide KOH, 22% (form in 2.20 situ soap with stearic acid) Octyl 2.50 2.50 2.50 2.50 methoxycinnamate Water B BAL BAL BAL BAL BAL BAL BAL BAL Glycerin B 1 1 1 1 1 1 1 1

EXAMPLE 12 Cell Based Assay

This example shows the skin lightening effect of using 4-methyl 7-hydroxy-coumarin derived resorcinol compounds as skin lightening agents in accordance with the inventive method. This experiment was carried out using a cell based assay.

B16 mouse melanoma cells were utilized in the following experiment to evaluate the efficacy of skin lightening agents. B16 cells were plated in 96-well microtiter plates at a density of 5000 cells per well and cultured overnight in Dulbecco's Modified Eagle's Medium (phenol red free) containing 10% fetal bovine serum and 1% penicillin/streptomycin at 37° C. in the presence of 5% CO₂. After 24 hours, the medium was replaced with fresh growth medium containing the treatments. All cultures were incubated for 72 hours at which time melanin was visible in the control treatment. The melanin-containing medium was transferred to a clean 96-well plate and quantified by reading the absorbency at 530-nm. Cell viability was assessed by measurement of lactate dehydrogenase levels to ensure the decrease in melanin was not a result of cellular toxicity.

TABLE 7 Compound % of Control (Skin Lightening Agent) Concentration (Melanin Synthesis) 7-hydroxy-3,4-dihydro- 6.25 micromolar 75.8% 4-methylcoumarin (B1) 4-Ethyl Resorcinol 6.25 micromolar 34.0% 3-(2,4-dihydroxyphenyl)- 6.25 micromolar 32.8% butyric acid (II) Methyl 3-(2,4- 6.25 micromolar 36.4% dihydroxyphenyl)- butyrate (D1)

From the results tabulated above it appears that coumarin derived resorcinol compounds of the present invention reduce melanin synthesis to about the same degree than 4-ethyl resorcinol.

EXAMPLE 13 Mushroom Tyrosinase Assay

Mushroom tyrosinase inhibition is indicative of reduction in melanin synthesis, thereby showing skin lightening effect. This experiment shows the efficacy of coumarin derived resorcinol derivatives of the present invention.

Into each well of a 96-well plate, 150 microliters of phosphate buffer (100 mM, pH 7.0), 10 microliters of L-DOPA (L-3, 4-Dihydroxyphenylalanine, 10 mM), and 20 microliters of skin lightening agent (dissolved in ethanol, which is the control) were added. Following an initial measurement of background absorbency at 475-nm, 20 microliters of mushroom tyrosinase (Sigma T-7755; 6050 units/ml) was added and incubated at room temperature.

Absorbency was read at 475-nm over the following time points: 0, 2, 4, and 6.5 minutes. The data is plotted as 475-nm absorbency vs. time (minutes) and the slope of the line is calculated (ΔAbs 475 nm/min). Values are expressed as the percentage of the respective untreated ethanol control reaction.

${\%\mspace{14mu}{of}\mspace{14mu}{Control}} = {\frac{\left( {{Reaction}\mspace{14mu}{rate}\mspace{14mu}{for}\mspace{14mu}{treated}\mspace{14mu}{reaction}} \right)}{\left( {{Reaction}\mspace{14mu}{rate}\mspace{14mu}{for}\mspace{14mu}{untreated}\mspace{14mu}{control}} \right)} \times 100\%}$

TABLE 8 % of Control Compound Concentration (Melanin Synthesis) 4-Ethyl Resorcinol  0.1 micro-M 72.7   1 micro-M 46.3   10 micro-M 30.8  100 micro-M 20.7 7-Hydroxy Coumarin  0.1 micro-M 104   1 micro-M 100   10 micro-M 108  100 micro-M 117 7-hydroxy-3,4-dihydro-   1 micro-M 94.2 4-methylcoumarin (B1) 1.56 micro-M 90.4 12.5 micro-M 70.4  100 micro-M 75.3 3-(2,4-dihydroxyphenyl)-   1 micro-M 73.3 butyric acid (II) 1.56 micro-M 41.6 12.5 micro-M 28.0  100 micro-M 20.6 Methyl 3-(2,4-   1 micro-M 73.1 dihydroxyphenyl)- 1.56 micro-M 39.3 butyrate (D1) 12.5 micro-M 35.8  100 micro-M 41.0

The data show that the coumarin derived compounds of formulas II and D1 are substantially as effective as 4-ethyl resorcinol, both compounds having good skin lightening effects. The 7-hydroxy-3,4-dihydro-4-methylcoumarin (B1) compound from which the compounds of the present invention may be derived is not effective in skin lightening, as measured by the mushroom tyrosinase assay.

EXAMPLE 14

This example illustrates an inventive process according to the present invention. R-groups are as previously defined hereinabove.

It should be understood that the specific forms of the invention herein illustrated and described are intended to be representative only. Changes, including but not limited to those suggested in this specification, may be made in the illustrated embodiments without departing from the clear teachings of the disclosure. Accordingly, reference should be made to the following appended claims in determining the full scope of the invention. 

1. A cosmetic method of skin lightening comprising applying to the skin a composition comprising: a. about 0.000001 to about 50% of a compound of general formula I

Where each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, acyl, or heteroalkyl groups; R₃ represents linear or branched, cyclic or acyclic, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heteroalkyl group; R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated, containing or not containing a heteroatom C₁-C₂₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, heteroalkyl, aryl, or heteroaryl group; and b. a cosmetically acceptable carrier.
 2. The method of claim 1, wherein said composition further comprises a sunscreen.
 3. The method of claim 2, wherein said sunscreen is a micronized metal oxide.
 4. The method of claim 1, wherein said compound is a 4-methyl 7-hydroxy coumarin derived resorcinol derivative.
 5. The method of claim 1, wherein said compound is a compound of formula II:


6. The cosmetic method of claim 1, wherein R₁ and R₂ both represent hydrogen.
 7. The cosmetic method according to claim 1, wherein said composition further comprises a skin benefit agent selected from the group consisting of alpha-hydroxy acids, beta-hydroxy acids, polyhydroxy acids, hydroquinone, t-butyl hydroquinone, Vitamin C derivatives, dioic acids, retinoids, resorcinol derivatives, and mixtures thereof.
 8. The cosmetic method of claim 1, wherein said composition further comprises an organic sunscreen selected from the group consisting of Benzophenone-3, Benzophenone-4, Benzophenone-8, DEA, Methoxycinnamate, Ethyl dihydroxypropyl-PABA, Glyceryl PABA, Homosalate, Methyl anthranilate, Octocrylene, Octyl dimethyl PABA, Octyl methoxycinnamate (PARSOL MCX), Octyl salicylate, PABA, 2-Phenylbenzimidazole-5-sulphonic acid, TEA salicylate, 3-(4-methylbenzylidene)-camphor, Benzophenone-1, Benzophenone-2, Benzophenone-6, Benzophenone-12, 4-Isopropyl dibenzoyl methane, Butyl methoxy dibenzoyl methane (PARSOL 1789), Etocrylene, and mixtures thereof.
 9. A cosmetic composition comprising: a. about 0.000001 to about 50% of a compound of general formula I:

wherein each or both R₁ and/or R₂ represents hydrogen (H); linear or branched, saturated or unsaturated C₁- C₁₂ alkyl, alkenyl, acyl, or heteroalkyl groups; R₃ represents linear or branched, cyclic or acyclic, saturated or unsaturated C₁-C₁₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, or heteroalkyl group; R₄ represents a hydrogen atom (H); straight or branched, cyclic or acyclic, saturated or unsaturated, containing or not containing a heteroatom C₁-C₂₂ alkyl, alkenyl, cycloalkyl, cycloalkenyl, heteroalkyl, aryl, or heteroaryl group; and b. a cosmetically acceptable carrier.
 10. The cosmetic composition of claim 9, wherein said compound is a compound of formula II:


11. The cosmetic composition of claim 9, wherein R₁ and R₂ both represent hydrogen.
 12. The cosmetic composition of claim 9, wherein said compound comprises about 0.00001% to about 10% of said composition.
 13. The cosmetic composition of claim 9, wherein said compound comprises about 0.001% to about 7% of said composition.
 14. The cosmetic composition of claim 9, wherein said compound comprises about 0.01% to about 5% of said composition. 